Learn Portuguese (Portugal): Tudo é caro aqui. - Everything is expensive here.

Tudo means "everything" and is the exact opposite of nada ("nothing"). Because tudo is an affirmative word, it doesn't use the negative word não. If you wanted to say the opposite using the double negative rule from this lesson, you could say Não é nada caro (It is not expensive at all).

What is the difference between tudo and todos?

Tudo means "everything" (referring to general things), while todos means "everyone" or "all of" specific things (like "all the houses"). Since we are talking about everything in general, we use tudo.

Why do we use the masculine adjective caro instead of the feminine cara?

The word tudo refers to an abstract concept ("everything"), so it does not have a specific feminine or masculine gender. In Portuguese, whenever there is no specific gender to agree with, we use the masculine singular form by default.

Why use é (from the permanent verb ser) if prices can change?